php - Why does email show accented characters as question marks?

If I have the following string in my MySQL database (FYI, Collation is utf8mb4_unicode_ci):

Bebé Elosúa Sierra
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It displays fine on my site if I echo it back using htmlentities, but if I send an email via AmazonSES, it shows up (at least in Gmail) like this.

It shows in the body of the email as:

Beb? Elos?a Sierra
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And more oddly, it shows in the subject of the email as:

Beb???????????? Elos????????????a Sierra
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Is there anyway to prevent this, or is it something on Google/Gmail's end that I have no control over?